title: Antibacterial properties of 2% lidocaine and reduced rate of endophthalmitis after intravitreal injection.
abstract: OBJECTIVE
  To determine whether the application of subconjunctival 2% lidocaine/0.1% methylparaben for anesthesia may reduce rates of endophthalmitis after intravitreal (IVT) injection.
  
  
  METHODS
  We performed in vitro experiments to determine the antibacterial properties of 2% lidocaine/0.1% methylparaben (lidocaine) against causative organisms of endophthalmitis. Isolates of Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus viridans from patients with endophthalmitis were incubated with or without lidocaine. Aliquots (100 µL) were plated on Mueller-Hinton (S. aureus and S. epidermidis) or blood agar plates (S. viridans) at 0, 10, 30, 120, and 240 minutes, and colonies were counted after 24 hours. A retrospective review of 15,042 IVT injections was performed from January 2004 to February 2011 to determine the rate of endophthalmitis with or without application of subconjunctival lidocaine for anesthesia.
  
  
  RESULTS
  Lidocaine demonstrated rapid bactericidal effects against all 3 organisms. After 10 minutes of exposure, there was approximately a 90% (P < 0.01), 95% (P < 0.001), and 92% (P < 0.001) reduction in colony forming units when compared with time 0 for S. aureus, S. epidermidis, and S. viridans, respectively. Complete elimination of colony forming units occurred at subsequent time points for each organism in contrast to logarithmic increase for control plates. There were a total of 0 cases of endophthalmitis of 6,853 IVT injections performed with subconjunctival lidocaine and 8 cases of endophthalmitis of 8,189 (0.1%) IVT injections performed with other methods of anesthesia (P = 0.03).
  
  
  CONCLUSIONS
  Application of subconjunctival 2% lidocaine/0.1% methylparaben for anesthesia may reduce the incidence of endophthalmitis after IVT injection.
authors.affiliation: *Department of Ophthalmology, Vanderbilt University, Nashville, Tennessee; †VA Tennessee Valley Healthcare System, Nashville, Tennessee; and ‡Department of Ophthalmology, Emory University, Atlanta, Georgia.
authors.forename: Aaron
authors.initials: A
authors.lastname: Tustin
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Kim
authors.forename: Amy
authors.initials: A
authors.lastname: Chomsky
authors.forename: G Baker
authors.initials: GB
authors.lastname: Hubbard
authors.forename: Jinsong
authors.initials: J
authors.lastname: Sheng
mesh_terms: D000779:Anesthetics, Local / Q000008:administration & dosage / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001431:Bacteriological Techniques; D015169:Colony Count, Microbial; D009877:Endophthalmitis / Q000188:drug therapy* / Q000382:microbiology; D015818:Eye Infections, Bacterial / Q000188:drug therapy* / Q000382:microbiology; D006801:Humans; D058449:Intravitreal Injections; D008012:Lidocaine / Q000008:administration & dosage / Q000494:pharmacology*; D010226:Parabens / Q000008:administration & dosage / Q000494:pharmacology; D011310:Preservatives, Pharmaceutical / Q000008:administration & dosage / Q000494:pharmacology; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000302:isolation & purification; D013212:Staphylococcus epidermidis / Q000187:drug effects / Q000302:isolation & purification; D013290:Streptococcal Infections / Q000188:drug therapy* / Q000382:microbiology; D034363:Viridans Streptococci / Q000187:drug effects / Q000302:isolation & purification
chemical_list: D000779:Anesthetics, Local; D000900:Anti-Bacterial Agents; D010226:Parabens; D011310:Preservatives, Pharmaceutical; D008012:Lidocaine; C015358:methylparaben